New Material Of The Ctenochasmatid Forfexopterus From Jehol Biota Of Western Liaoning

Over the past two decades,the Early Cretaceous Jehol Biota in western Liaoning,China,have discovered a large number of beautifully preserved fossils,such as feathered dinosaurs,early birds,early mammals and angiosperms.Of these,pterosaur fossils are also flourished,providing an opportunity to understand the faunal turnover of this lineage.Ctenochasmatids are dominant in the pterosaur assemblage of Jehol Biota.The discovery of a large number of fossils has facilitated the study of the skeletal anatomy,taxonomic diversity and ecological habits of Ctenochasmatidae.Here,two specimens of the ctenochasmatid Forfexopterus from Jehol Biota of western Liaoning,are described and discussed in osteology,taxonomy,paleohistology,and tooth replacement.The specimen(SDUST-V1003)was preserved with the right wing skeleton,showing the single autoapomorphy of Forfexopterus(the first wing phalanx shorter than the second,and longer than the third).However,this specimen has a mature ossification,only 75%of the subadult holotype of Forfexopterus in wingspan.This mature is also supported by the histological information.This discrepancy indicates a developmental plasticity of Forfexopterus,but its relationship with the sexual dimorphism needs to be certain by more available material.The second specimen(SDUST-V1007)is rostral part of the mandible,with the typical tooth morphology and arrangement of the Ctenochasmatidae,and has a tooth density of 2.2 teeth/cm comparable with that of Forfexopterus.The tooth replacement of SDUST-V1007 is well identified by CT scan and 3D reconstruction,such as,three developmental stages,Zahnreihen identified,Z-spacing is 2,and the tooth replacement pattern is simple alternation between every second positions.These information is different from the ornithocheirid Coloborhynchus,possibly effected by the different feeding strategy between the ornithocheirids and ctenochasmatids.This study provides more useful information in development,paleohistology and tooth replacement for the future in the study of the pterosaur assemblages of the Jehol Biota.